Method of automatically packaging radio active sources and apparatus therefor

ABSTRACT

An automatic method of packing radioactive sources, the method mainly comprising moving a circular tray automatically and periodically in a shielded enclosure past a number of equidistant working stations arranged in a circle and corresponding to the various respective stages of packaging and to supervisory operations, the tray being formed with equidistant peripheral perforations to the number of working stations, a logic circuit initiating, for each perforation, the starting or not starting of a working station in dependence upon the result output by the immediately preceding working station.

Hittite tates Patent n et al.

[54] METHOD OF AUTOi -'=TKCALLY PACKAGING I =l AC SOURCES AND P TUS REFOR Inventors: Jean E-adin, 4 bis, rue Blanche, 92 Bois Colombes; Paul Lengagne, 2, rue de Rouen, 92 Nanterre, both of France Filed: Mar. 5, 1970 Appl. No.: 16,780

Foreign Application Priority Data Mar. 1 1, 1970 France ..6906546 US. Cl ..53/53, 53/78, 53/83,

53/282, 252/301 .1 Int. Cl ..B65b 57/00 field ofSearch ..53l53, 78, 83,282

[56] References Cited UNITED STATES PATENTS 2,435,747 2/1948 Larson ..53/83 X 3,440,797 4/1969 Spielmann ..53/83 Primary Examiner-Travis S. McGehee Attorney-Cameron, Kerkam & Sutton 57 ABSTRACT An automatic method of packing radioactive sources, the method mainly comprising moving a circular tray automatically and periodically in a shielded enclosure past a number of equidistant working stations arranged in a circle and corresponding to the various respective stages of packaging and to supervisory operations, the tray being formed with equidistant peripheral perforations to the number of working stations, a logic circuit initiating, for each perforation, the starting or not starting of a working station in dependence upon the result output by the immediately preceding working station.

8 Claims, 10 Drawing Figures Patented May 23, 1972 3,664,083

4 Sheets-s 1 All" Patented May 23, 1972 4 Sheets-Sheet 2 Patented May 23, 1972 3,664,083

4 Sheets-Sheet 5 Patented ay 23, 1972 4 Sheets-Sheet 4 FIGS METHOD OF AUTOMATICALLY PACKAGING RADIO ACTIVE SOURCES AND APPARATUS THEREFOR This invention relates to a method of automatically packaging radioactive sources and to an apparatus for performing the method and to the sealed radioactive sources prepared thereby, the sources possibly being very small, for instance, 1.5 mm in diameter and 3.5 mm in overall length, and being for use, for instance, in gynaecological contact radium therapy equipment.

Large-scale production of sealed radioactive sources i.e., sources comprising a radioelement or a radioactive compound enclosed in a sealed capsule gives rise to difficulties in that the material to be processed is radioactive, so that all the packaging operations must be perfonned behind heavy lead shielding, manual operations being precluded. The difficulties increase if the radioactive element to be packed is very small, for the packaging operations then require great care.

The method according to the invention is to automate the various steps in the packaging of radioactive sources in accordance with a preset logic program. The method according to the invention has the advantage of making it unnecessary for operators to work in unpleasant conditions, of cutting out mistakes during handling, of providing a very uniform product and a high output, and of eliminating faulty items from the output.

More particularly, this invention relates to an automatic method of packing radioactive sources, the method mainly comprising moving a circular tray automatically and periodically in a shielded enclosure past a number of equidistant working stations arranged in a circle and corresponding to the various respective stages of packaging and to supervisory operations, the tray being formed with equidistant peripheral perforations to the number of working stations, a logic circuit initiating, for each perforation, the starting or not starting of a working station in dependence upon the result output by the immediately preceding working station.

The invention also relates to an apparatus for automatically packing radioactive sources according to such method, mainly characterized in that it comprises a circular tray which can rotate around its axis relatively to a frame and whose rotation is controlled by a set of solenoid valves, the tray being formed on its periphery with equidistant perforations, the apparatus comprising working stations to the number of perforations, the working stations being rigidly secured to the frame and distributed regularly around the tray periphery so that when any one station is above a tray perforation, each other station is above another perforation in the tray, each working station carrying out a step in the packaging operation or a supervisory operation until the step in which the sealed radioactive sources are ejected from the apparatus, the same comprising a logic circuit controlled by the working stations which transmit signals to the logic circuit, the same being so devised that for each tray perforation, each working station determines the advisability of starting the next working station upon the subsequent arrival thereat of such perforation.

The invention also relates to sealed radioactive sources prepared by means of such method, the sources being mainly distinguished in that they comprise a metal envelope closed at both ends by at least one welded metal ball, the envelope containing a grain of a radioactive element or radioactive compound.

Other features of the invention will be disclosed by the following explanatory non-limitative description of an embodiment, reference being made to the accompanying drawings wherein:

FIG. 1 shows a sealed radioactive source according to the invention;

FIG. 2 is a diagrammatic view in developed form showing the various tray perforations and the corresponding working stations P, to P FIG. 3 shows the first working station P, but also applies basically to the stations P and P FIG. 4 shows the second station P FIG. 5 shows some of station P FIG. 6 shows some of station P FIG. 7 shows station P with details of the gripper system;

FIG. 8 shows an alternative form of station P and FIGS. 9 and 10 show two alternative supply facilities for station P,, FIG. 9 showing a vertical loader and FIG. 10 showing a horizontal loader.

Referring to FIG. 1, a sealed radioactive source is shown in the form of a metal envelope 1 containing a grain 2 of radioactive compound and closed by a metal ball 3 welded as indicated by the reference 4.

Tray 5 of the apparatus according to the invention is shown in developed form in FIG. 2 but is in fact circular.

The system formed by tray 5 and the working stations of which there are eight in the present case is received in a hermetic enclosure (not shown) which is shielded (by 50 or mm of lead) and which backs on to another enclosure (not shown) in which radioactive grains eg of pollucite. which is a cesium silicoaluminate, are prepared by pressing, sintering and machining. The grains are conveyed by a vibrator to the automated enclosure and are returned by vibrator to the first enclosure after they have been packed into sealed sources.

The packing apparatus according to the invention comprises a rotating tray or table or the like, eight working stations and a logic drive, supervisory and safety facility.

The indexing rotating tray is driven by a pneumatic actuator (not shown) and can take up eight positions; it is formed on its periphery with eight equidistant perforations representing eight working positions each receiving a bottom welding electrode gripper 6, more details of which can be seen in FIG. 7. Tray 5 is rotated by a pneumatic actuator driven and controlled by a set of solenoid valves. A 24-volt AC signal brings each working position exactly opposite a working station.

The functions of the eight consecutive working stations P, to P are as follows: at P,, supply of stainless steel envelopes l to tray 5, positioning of an envelope 1 in a device 6 of the tray (each perforation or working position of the tray initially has a device 6); at P a check on whether the envelope 1 is present and is correctly orientated i.e., with its blind aperture facing upwards; at P supply of radioactive grains 2 and filling of envelope 1 with a single grain 2; at P,, a check to ensure that the grain 2 does not exceed the required maximum height; at P a check that the grain 2 is actually in the envelope 1 and is of the correct height; at P a supply of steel covering balls 3 and the placing of a ball 3 on the steel casing 1 containing a radioactive grain 2; at P welding together of the ball 3 and envelope 1; and at P delivery of the finished sealed sources, and of unwelded envelopes with or without a grain 2, to different storage places.

The good indexing of the tray 5 is accurate enough to cope with the reduced diametric clearance of from 0.1 to 0.2 mm between the envelope 1 and the grain 2 and also enables the speed of tray rotation to be so controlled that the ball 3 does not leave its position when changing stations for welding.

The devices 6 are in three parts a central part in the form of a divided copper cone 7, a cylindrical annular portion 8 having a female cone in which the first part is positioned, and a spring 9 which bears the system. With the spring uncompressed, the device 6 is free, does not clamp and is near the top of the tray 5. The spring 9 is compressed only at station P (welding), at which the device 6 serves both as a gripper and becomes rigidly connected to the bottom electrode 10 of a resistance welding facility.

The eight working stations P, to P hereinbefore described operate as follows:

Station P, (supply of steel envelopes):

The envelopes 1 can be supplied in two different ways:

a. Automatically by a vibrating bowl as shown in FIG. 3. In this event there is a 50 percent chance of the envelope being wrongly positioned (with its opening facing downwards); this does not disturb the process since the misorientation is detected at station P which cancels the operations programmed by the logic circuit, the envelope returning to the vibrating bowl whence it came. The disadvantage of this system is that it halves the rate of manufacture. With this kind of feed, the vibrating bowl (not shown) delivers envelopes 1 to a tube 11. A solenoid 12 moves a slider 13; envelope 1 drops into a pocket 14 in slider 13 which returns to its initial position, whereafter piston 15 delivers envelope 1 to device 6. A fresh envelope 1 at the end of tube 11 and immediately opposite slider 13 is ready for the next operation.

b. Or semi-automatically, with manual filling of a loader which supplies a distributor either by gravity or at pressure. With manual filling of the loader, the envelopes 1 have a high probability of being orientated correctly. FIG. 9 shows a vertical loader 16 used instead of vibrating bowl feeding. A spring 17 urges casings 1 against slider 13. FIG. 10 shows a horizontal loader 18.

Station P (checking on envelope orientation, see FIG. 4).

This check is made by means of a needle 19 which, ifthe envelope is positioned correctly i.e., with its opening at the top penetrates thereinto. If the envelope is incorrectly positioned, needle 19 strikes the end of casing 1 and compresses spring 20 which transmits its movement to the envelope 1. If the needle 19 can penetrate into the envelope 1, a moving magnetic contact 21 rigidly secured to needle 19 closes a circuit and transmits a signal to the logic circuit which then prepares the next operations.

Checking for whether or not the envelope is present in the device 6 is done in the same way at a second (lower) position of the needle and by means of a second contact (not shown).

Station P (supply of radioactive grains).

Similarly to what occurs in the case of station P (FIG. 3), the grains 2 are supplied by means of a vibrating bowl 27 which delivers grains to a distributor and aligns them therein. In a variant, shown in FIG. 8, a grain 2 is removed by suction through a duct 26 from the bottom of the distributor and goes to a slider operated by a solenoid and is vehicled to a slope 25 along which the grain drops into the steel envelope 1. This kind of suction vehicling may also be of use at station P, for conveyance of the envelopes, the suction having to be adjusted so that the envelope 1 does not jam.

Station P (check on maximum height ofgrain).

Some of station P is shown in FIG. 5. A check similar to the check given at station P (FIG. 4) is made at station P except that needle 19 terminates in a tip 22 having the same characteristics as the ball 3 which will be welded subsequently to seal the envelope. lf the tip 22 can actually take up the position of the ball, the grain 2 cannot be in excess of the proper height. A contact on needle 19 initiates the next sequences of events. At station P in contrast to what happens at station P the checking is by direct contact between needle 19 and casing 1. The whole of station P must therefore be insulated from the frame of the apparatus by an insulating plate 23, for instance, of polythene; the plate 23 is shown in FIG. 4 but is used only at station P Station P (checking for presence of grain and for minimum height of grain).

Some ofstation P is shown in FIG. 6, but FIG. 4 still applies since the check given at station P is similar to the check given at station P the only difference being that the sensor does not descend so far. The needle touches a grain 2 of appropriate height to trigger off the sequence of logic operations. If the needle 19 makes half its stroke, a grain is present but is too short, in which event a contact cancels the sequence of operations.

Station P (supply of balls).

Supply is either by gravity or by vibrating bowl. The balls 3 drop on to a slider, which takes a ball and places it on the lips of the envelope by way of a positioning duct, the movement being produced by an electromagnet. The balls 3 are supplied by the vibrating bowl in just the same way as the supply of envelopes in FIG. 3.

Station P (welding of ball and envelope system).

The welding station is e.g. a 5 kVA resistance welding facility. Welding is performed in an argon atmosphere (2 liters/minute) with a force of 20 newtons and for 0.04 second (two periods).

For this welding step 10, which is shown in FIG. 7, the bottom electrode makes contact with the cylindrical part 8 of the spring-biased device 6. The top of the machine (top and bottom electrodes) is installed in the shielded enclosure containing the complete apparatus according to the invention, and the body of the machine (power, drive and supervisory facili ties) is outside the enclosure. The machine is driven by a pneumatic actuator driven by a set of solenoids (not shown). At the beginning of welding, the top electrode 24 descends to keep the ball 3 in bearing engagement of the envelope lips and to engage the central portion 7 of device 6 in the annular portion 8 thereof, so that the article to be welded is clamped and contact is made until the clamping force reaches the preset value, whereupon the welding current is switched off and a signal is transmitted to the logic circuit which initiates the next step.

Station P (delivery or ejection of articles).

Since the devices 6 are drilled right through, the articles can be ejected by compressed air. The ejection station has a slider formed with two or three apertures.

a. When the source is sealed i.e., when the source has been appropriately filled and welded the logic program has no effect on slider position and the source is ejected through one of the slider apertures by compressed air.

b. When the source has not been completed (absence of grain, grain too high, grain too short, absence of ball), the sequence has been interrupted by one of the stations and the interruption causes the slider to move towards the second aperture (such movement is produced by an electromagnet) via which the faulty items are ejected to a storage facility.

c. The slider can take up a further position in the case in which the station P automatically loads the tray with envelopes. Wrongly oriented envelopes are ejected through this third aperture at the end of the sequence to return to the vibrating distributor bowl of station P The logic drive, supervisory and safety facility (not shown) of the apparatus according to the invention is very simple, comprising dynamic relays, reversing switches, contactors, electromagnets and a control ofthe off-load circuit. It can perform all the sequences of the program for the manufacture hereinbefore described. The control stations either allow following sequences to be linked together in the order of manufacture or do not allow such linking together.

In the event of any anomaly occurring at any working station, the operating cycle can be stopped by safety features.

This invention has of course been hereinbefore described by way of explanation but without limitation and details can be modified without departing from the scope of the invention. More particularly, of course, the method according to the invention is of use for making sources of a material other than pollucite, and the form of sealing may be other than what has been described. More particularly, the envelope can take the form ofa cylinder open at both its ends.

We claim:

1. An apparatus for automatically packaging radioactive sources, comprising a frame, a tray provided on its periphery with equidistant perforations arranged in a circle and each containing a gripper, equidistant working stations rigidly secured to said frame and arranged in a circle, the number of said stations being equal to that of said perforations, so that, when any one of said stations is above one of said perforations, each other station is above another of said perforations, means for causing said tray to rotate around its axis relatively to said frame, said working stations including, in succession, at least a first station provided with first distributing means for supplying metal envelopes to said tray and positioning an envelope in one of said grippers, a second station provided with a first needle adapted to move towards said tray and carrying a first contact adapted to transmit a signal, a third station provided with second distributing means for supplying radioactive grains and filling said envelope with one grain, a fourth station for checking maximum grain heights, said fourth station being provided with a second needle adapted to move towards said tray and carrying a second contact adapted to transmit a signal, a fifth station for detecting the presence of a grain in said envelope and for detecting grain heights, said fifth station being provided with a third needle adapted to move towards said tray and to transmit a signal, a sixth station provided with third distributing means for supplying metal balls and placing a ball on said envelope, a seventh station for welding the ball to said envelope, said seventh station being adapted to transmit a signal and comprising a first electrode which is lowered onto said ball, and a second electrode which is disposed below said tray and which engages with the gripper located thereabove so as to become electrically connected thereto, an eighth station comprising a slider with at least two orifices for the ejection of finished sealed sources and faulty sources, respectively, said signals contingently transmitted by said second, fourth, fifth and seventh working stations determining the starting of the next working station upon the arrival thereat of a perforation of said tray.

2. An apparatus according to claim 1, wherein, at said first station, a vibrating bowl is adapted to supply said envelope automatically, and an electromagnetically operated pusher is adapted to collect an envelope supplied by said vibrating bowl, then to tip such envelope into the grippers located in the tray perforations.

3. An apparatus according to claim 1, wherein, at said first station, the supply of envelopes is semi-automatic by a manually filled loader.

4. An apparatus according to claim 1, wherein, at said third station, a vibrating bowl is adapted to supply the radioactive grains.

5. An apparatus according to claim 1, wherein a suction device is adapted to supply the radioactive grains.

6. An apparatus according to claim 1, wherein, at said second station, said contact is a magnetic contact providing a signal, if said first needle drops to the bottom of the envelope.

7. An apparatus according to claim 1, wherein. at said fourth station, said second needle terminates in a tip having the same shape as the ball to be welded to the envelope 8. An apparatus according to claim 1, wherein. at said sixth station, a vibrating bowl supplies the balls. 

1. An apparatus for automatically packaging radioactive sources, comprising a frame, a tray provided on its periphery with equidistant perforations arranged in a circle and each containing a gripper, equidistant working stations rigidly secured to said frame and arranged in a circle, the number of said stations being equal to that of said perforations, so that, when any one of said stations is above one of said perforations, each other station is above another of said perforations, means for causing said tray to rotate around its axis relatively to said frame, said working stations including, in succession, at least a first station provided with first distributing means for supplying metal envelopes to said tray and positioning an envelope in one of said grippers, a second station provided with a first needle adapted to move towards said tray and carrying a first contact adapted to transmit a signal, a third station provided with second distributing means for supplying radioactive grains and filling said envelope with one grain, a fourth station for checking maximum grain heights, said fourth station being provided with a second needle adapted to move towards said tray and carrying a second contact adapted to transmit a signal, a fifth station for detecting the presence of a grain in said envelope and for detecting grain heights, said fifth station being provided with a third needle adapted to move towards said tray and to transmit a signal, a sixth station provided with third distributing means for supplying metal balls and placing a ball on said envelope, a seventh station for welding the ball to said envelope, said seventh station being adapted to transmit a signal and comprising a first electrode which is lowered onto said ball, and a second electrode which is disposed below said tray and which engages with the gripper located thereabove so as to become electrically connected thereto, an eighth station comprising a slider with at least two orifices for the ejection of finished sealed sources and faulty sources, respectively, said signals contingently transmitted by said second, fourth, fifth and seventh working stations determining the starting of the next working station upon the arrival thereat of a perforation of said tray.
 2. An apparatus according to claim 1, wherein, at said first station, a vibrating bowl is adapted to supply said envelope automatically, and an electromagnetically operated pusher is adapted to collect an envelope supplied by said vibrating bowl, then to tip such envelope into the grippers located in the tray perforations.
 3. An apparatus according to claim 1, wherein, at said first station, the supply of envelopes is semi-automatic by a manually filled loader.
 4. An apparatus according to claim 1, wherein, at said third station, a vibrating bowl is adapted to supply the radioactive grains.
 5. An apparatus according to claim 1, wherein a suction device is adapted to supply the radioactive grains.
 6. An apparatus according to claim 1, wherein, at said second station, said contact is a magnetic contact providing a signal, if said first needle drops to the bottom of the envelope.
 7. An apparatus according to claim 1, wherein, at said fourth station, said second needle terminates in a tip having the same shape as the ball to be welded to the envelope.
 8. An apparatus according to claim 1, wherein, at said sixth station, a vibrating bowl supplies the balls. 